Acid-sensing ion channels (ASICs) play vital roles in numerous physiological processes and are implicated in pathological conditions characterised by low pH, such as ischemia and inflammation. Selectively inhibiting ASICs has shown promise in reversing associated pathologies, but current approaches to developing selective and potent ligands through functional screening and nanobody generation have limitations, often due to the complexity of these large, multimeric, transmembrane proteins. In this project we focus on the soluble "thumb" domain, a highly structured segment and the primary extracellular ligand binding domain of existing nanobody and peptidic ASIC1 ligands. Currently, there are very few selective and potent ligands targeting ASIC2 and ASIC3. By leveraging the simplicity, stability, ligand-binding competence, and small size of this functional ligand binding hotspot, we aim to explore new approaches for generating selective ASIC ligands, including small molecules, cyclic peptides, and nanobodies against all ASIC isoforms. By identifying novel ligands, this approach could lead to the development of safe and effective drugs for treating a range of inflammatory and ischemic conditions. Our proposal builds on unpublished work showing that the ASIC thumb domain maintains its fold and ligand binding properties in isolation, providing a completely new approach to drug development against this class of ion channels.
